Bone implants are widely known at present.
One of the most popular bone implants is a bone implant in the form of an apertured plate having a smooth support surface. Since the early 20th century, bone plates and screws have been used for internal fixation of broken bones. As of the late 1980's, locking bone plates were developed. A locking bone plate is provided with a locking screw having the threads on an outer surface of its head which are mated with the corresponding threads in the bone plate hole. Because of the fixed relationship between the locking screws and the bone plate, said locking screws appear to be highly resistant to shear or torsional forces. Thus, the main feature of such “locking bone plates” is a solid fixation between the plate and the inserted screws. The advantages of locking plates of the kind such as their angular stability, less bone vascular damage, improved resistance to infection proved as quite evident. Since then, the use of locking plates has exploded, and at present they are produced by different manufacturers (WO 2007/123655, 2007 November 2001).
A critical widely-known problem of the above-described bone implants is the development of periosteum necrosis and osteoporosis of the bone just beneath the locking plate.
As it is described in “New Bio-conception of Bone Regeneration. Analysis>>//Original Instruments and Implants for Study of Internal Fixation. Review. AO/ASIF “SYNTHESIS”, 1991, p. 4, osteoporosis of the bone beneath the plate is a direct result of blood supply deficiency in the outer layer of the bone caused by the contact with an implant which depends on the surface area of said contact. Thus, it was concluded that the decrease of the surface contact area between the plate and the bone results in the improvement of the blood supply. An undisturbed blood supply promotes bone regeneration, lessens the risk of infection as well as helps to prevent bone necrosis and early osteoporosis.
The above-described conclusion was taken as the ground in the development of dynamic bone implants described for example, ib., page 6 and also in SU940759, published 7 Jul. 1982, RU 2334483, published 27 Sep. 2008, BY556U, published 30 Jun. 2002. The support surface of said dynamic implants is made with the recesses of various configuration positioned in a pre-defined order. The surface of such grooves has no contact with the bone, this resulting in no damage to blood supply in the areas in question. However, the problem of osteoporosis in dynamic implants is far from being solved, since between the grooves there is still a sufficiently large surface area that continuously remains in close contact with the bone.
The nearest prior art reference of an implant according to the invention is a bone implant described in WO 2007/047420, published 26 Apr. 2007. A bone implant described in the above publication is made as an apertured plate having a support surface and is located within a sleeve from a bio-compatible material, at least partially from caprolactam, which is impregnated with pharmaceutical substances.
The nearest prior art reference of a spacer according to the invention is a sleeve described in WO 2007/047420, published 26 Apr. 2007, which is made from a bio-compatible material, at least partially from caprolactam, and is impregnated with pharmaceutical substances. The above-described sleeve is intended for dressing on a bone implant and further placing onto a fractured bone. The sleeve can be made both from a bio-degradable material and a bio-stable material. The period of bio-degradation makes up to 6 months until a bone implant is removed by surgical means.
It should be noted, however, that the technical decisions described in WO 2007/047420 also do not make it possible to completely solve the problem of periosteum necrosis and osteoporosis, since the surface of the sleeve locked between a bone and a support surface of a plate is held in close contact with the bone for a continuous time. Besides, a sleeve from a bio-stable material features some additional disadvantages resulting from the fact that said sleeve is dressed upon both a support surface of an implant and its non-support surface. Firstly, the pharmaceutical substances for the treatment of the osseous tissue are not intended for the supply into the soft tissue and may adversely affect the latter. Secondly, by the moment the bone implant is to be removed by surgical means the soft tissue might grow into the portion of the sleeve that is dressed upon a non-support surface of the plate, this substantially complicating the surgical removal of a bone implant.
The nearest prior art reference of a method according to the invention is a method of surgical treatment described in WO 2008/113191, published 25 Sep. 2008 (Brief Description of the Surgical Procedure). A method of treatment a fractured bone by means of placing a bone implant made as an apertured plate having a support surface consists in fixing a bone implant to the fractures of the bone by screwing the fixing screws into said bone through the respective apertures in an implant plate. This method also features the same critical disadvantage of the bone implants of the kind i.e. the incidence of periosteum necrosis and osteoporosis of the bone just beneath the locking plate.
Thus, the contradiction that arises in this connection is quite evident. To perform the right fixation of the bone the contact of a bone implant with said bone is quite essential, while at the same time said contact results in complications such as periosteum necrosis and osteoporosis of the bone.